Joe Exotic says he's at the end of his rope, and might not be around much longer if he doesn't get some immediate help from President Trump ... or Cardi B ... or Kim Kardashian. TMZ's obtained a letter penned by the imprisoned 'Tiger King' star this week to his "Supporters, Fans, Loves Ones." He opens by saying the pandemic's over, so he's asking POTUS to grant him a miracle and free him ... but it's pretty bleak from there.